Don't most single story houses have insulation above the sheetrock that is hanging from the rafters?

Yes, sort of. You're confusing terms here. Your rafters are the sloped members that frame the pitch of the roof. Your ceiling joists are the horizontal members that frame the ceiling, and the sheetrock is attached to them. Rafters are not typically insulated unless you have a pitched ceiling that follows the pitch of the roof. Ceiling joists are always insulated.

Around here, most ceilings are insulated with blown-in cellulose. It is inexpensive and easily done by a DIY-er. The thickness depends on climate and local requirements. I wouldn't suggest insulating your rafters in too many circumstances.

Yes, sort of. You're confusing terms here. Your rafters are the sloped members that frame the pitch of the roof. Your ceiling joists are the horizontal members that frame the ceiling, and the sheetrock is attached to them.

Thanks for clearing that up.

Quote:

Rafters are not typically insulated unless you have a pitched ceiling that follows the pitch of the roof. Ceiling joists are always insulated.

I actually DO have that on one side of the room, so I will be needing to insulate the rafters there. What is the 'careful' installation method for insulating the rafters?

You need to maintain an inch and a half clearance minimum between the bottom of the roof deck and the top of your insulation. That space is for airflow. And you need to be sure you don't block any ventilation from the soffit into the that clearance space, otherwise you'll end up with condensation issues. Without that airspace, moisture will get trapped and will condense and saturate your insulation, damge the ceiling, rot things and generally cause you nightmares. Insulating spaces like that are pretty tough to do in a retrofit. You can't just blow that space full of cellulose fiber or stuff it full of fibreglass. Same with insulating your flat ceilings. Don't put insulation out into the eaves that reaches the roof deck and blocks ventilation from the soffit.

You need to maintain an inch and a half clearance minimum between the bottom of the roof deck and the top of your insulation. That space is for airflow. And you need to be sure you don't block any ventilation from the soffit into the that clearance space, otherwise you'll end up with condensation issues. Without that airspace, moisture will get trapped and will condense and saturate your insulation, damge the ceiling, rot things and generally cause you nightmares. Insulating spaces like that are pretty tough to do in a retrofit. You can't just blow that space full of cellulose fiber or stuff it full of fibreglass. Same with insulating your flat ceilings. Don't put insulation out into the eaves that reaches the roof deck and blocks ventilation from the soffit.